Why GridView RowUpdating Event is not giving the updated values?

Debugger Inside GridView RowUpdating Event

Debugger Inside GridView RowUpdating Event


This is a most common question in Forums. We will find the actual cause, for which the RowUpdating Event behaves abnormal.

Walk Through

  1. Add a GridView in aspx page and define all its required properties and Events.
    <asp:GridView ID="gvTestGrid" runat="server" AutoGenerateColumns="false" 
                  OnRowCancelingEdit="gvTestGrid_RowCancelingEdit"
                  OnRowEditing="gvTestGrid_RowEditing" 
                  OnRowUpdating="gvTestGrid_RowUpdating">
        <Columns>
            <asp:BoundField DataField="Column1" HeaderText="Some Column"/>
            <asp:CommandField ShowEditButton="true" />
        </Columns>
    </asp:GridView>
    
  2. Bind the GridView from back end. For our example, we will bind one DataTable.
    private void BindGrid()
    {
        // Add Column for the DataTable.
        DataTable dt = new DataTable();
        dt.Columns.Add(new DataColumn("Column1"));
    
        // Add Rows to DataTable.
        for (int i = 1; i < 5; i++)
        {
    	    DataRow dr = dt.NewRow();
    	    dr["Column1"] = "Old Value" + i;
    	    dt.Rows.Add(dr);
        }
    
        gvTestGrid.DataSource = dt;
        gvTestGrid.DataBind();
    }
  3. Define the GridView Events for Edit and Update operation.
    protected void gvTestGrid_RowEditing(object sender, GridViewEditEventArgs e)
    {
        //Set the edit index.
        gvTestGrid.EditIndex = e.NewEditIndex;
    
        //Bind data to the GridView control.
        BindGrid();
    }
    
    protected void gvTestGrid_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        //Get the new Values.
        GridViewRow row = gvTestGrid.Rows[e.RowIndex];
        string column1Value = ((TextBox)row.Cells[0].Controls[0]).Text;
    
        // Code to update the DataSource.
        //.....
    
        //Reset the edit index.
        gvTestGrid.EditIndex = -1;
    
        //Bind data to the GridView control.
        BindGrid();
    }
    
    protected void gvTestGrid_RowCancelingEdit(object sender, 
                                               GridViewCancelEditEventArgs e)
    {
        //Reset the edit index.
        gvTestGrid.EditIndex = -1;
    
        //Bind data to the GridView control.
        BindGrid();
    }
    
  4. GridView on Browser would look like…

    GridView on Browser

    GridView on Browser

    Now, Let’s Test

    To test the Edit and Update features, let’s click on Edit Button in any Row. We can see that GridView adds TextBoxes in all the cells of that Row immediately. It also shows you Update and Cancel Buttons where it was previously showing Edit Button.
    Let’s do some editing in the cells and click Update Button.

    GridView Cell Showing Updated Value

    GridView Cell Showing Updated Value


    It hits the breakpoint, we have set inside the RowUpdating Event. If we move our mouse on to the variables, which hold the cell values, we can see the old value instead of new updated value (Refer the debugging Screen Shot at the Top). So, we are stuck now, this is the bug.

    What to do now?

    Don’t panic. We need to find out what exactly in code is helping RowUpdating Event to give old values. So, the most wild guess is that, something is causing the Grid to bind again before RowUpdating Event, as we initially did during load.

    If you remember, in Step-2, we did bind the Grid, which is actually called on the Page Load like…

    protected void Page_Load(object sender, EventArgs e)
    {
        BindGrid();
    }
    

    According to the Event Life Cycle, when any Control Event is fired (here Grid RowUpdating), it first goes to Page Load. As it is coming to Page Load, so it calls the Bind method again and re-binds the Grid. Now, it goes to RowUpdating Event, but the updated values are lost because Grid is already reset in Page Load.

    So, How to Resolve?

    IsPostBack() is the answer. We have to check if the Page is posted back or not. If not, then we will bind the Grid.

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindGrid();
        }
    }
    

    Go and Share this with your friends

    This issue sometimes kills time. So, don’t wait, just share with everybody you know, who can understand this. Also provide your valuable feedback here. Thanks for reading.

ASP.NET Repeater with jQuery Slider

Image Slider with Repeater

Image Slider with Repeater


In this Blog, we will learn how to integrate one jQuery Slider Plugin with the ASP.NET Repeater Control.

Background

There was a question on implementation of slider with ASP.NET DataList Control and the guy who posted that was facing issues. The issue was actually due to the DataList control, which was rendering as HTML tables breaking the default jQuery Slider functionality. After researching a bit, I found that, it is very easy to implement this with the ASP.NET Repeater control. Let’s go step by step and learn.

Step by Step

Step-1 : Download jQuery Slider Plugin

You can take any jQuery Slider, but you need to see how exactly it allows contents inside it. For this example, we will be using the Elastislide. Hit the “Download Source” button on the page to download the zip file containing the Plugin files. We will try to implement the demo given here (Example 1).

Let’s extract the zip file. You will have something like this inside the Extracted folder.

Extracted jQuery Slider Files

Extracted jQuery Slider Files


So, here we can find all related JavaScript, CSS and images used for the Demos. The demo, which we will implement with Repeater is shown inside the index.html (highlighted in image). You can directly run and see in browser.

Step-2 : Analysis of Demo HTML Page

JavaScript and CSS Files Included

In Head section…

<link rel="stylesheet" type="text/css" href="css/demo.css" />
<link rel="stylesheet" type="text/css" href="css/elastislide.css" />
<link rel="stylesheet" type="text/css" href="css/custom.css" />
<script src="js/modernizr.custom.17475.js"></script>

In Body Section…

<script type="text/javascript" 
        src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js">
</script>
<script type="text/javascript" src="js/jquerypp.custom.js"></script>
<script type="text/javascript" src="js/jquery.elastislide.js"></script>

So, we will also include these files in our aspx page.

HTML Markup for Image Slider

If you open and see the index.html page, you will find a HTML structure which loads all the images. (I have removed the not needed headers and other HTML.)

<div class="container demo-1">
	<div class="main">
		<!-- Elastislide Carousel -->
		<ul id="carousel" class="elastislide-list">
			<li><a href="#"><img src="images/small/1.jpg" alt="image01" /></a></li>
			<li><a href="#"><img src="images/small/2.jpg" alt="image02" /></a></li>
			<li><a href="#"><img src="images/small/3.jpg" alt="image03" /></a></li>
			<li><a href="#"><img src="images/small/4.jpg" alt="image04" /></a></li>
			<li><a href="#"><img src="images/small/5.jpg" alt="image05" /></a></li>
			<li><a href="#"><img src="images/small/6.jpg" alt="image06" /></a></li>
			<li><a href="#"><img src="images/small/7.jpg" alt="image07" /></a></li>
			<li><a href="#"><img src="images/small/8.jpg" alt="image08" /></a></li>
			<li><a href="#"><img src="images/small/9.jpg" alt="image09" /></a></li>
			<li><a href="#"><img src="images/small/10.jpg" alt="image10" /></a></li>
			<li><a href="#"><img src="images/small/11.jpg" alt="image11" /></a></li>
			<li><a href="#"><img src="images/small/12.jpg" alt="image12" /></a></li>
			<li><a href="#"><img src="images/small/13.jpg" alt="image13" /></a></li>
			<li><a href="#"><img src="images/small/14.jpg" alt="image14" /></a></li>
			<li><a href="#"><img src="images/small/15.jpg" alt="image15" /></a></li>
			<li><a href="#"><img src="images/small/16.jpg" alt="image16" /></a></li>
			<li><a href="#"><img src="images/small/17.jpg" alt="image17" /></a></li>
			<li><a href="#"><img src="images/small/18.jpg" alt="image18" /></a></li>
			<li><a href="#"><img src="images/small/19.jpg" alt="image19" /></a></li>
			<li><a href="#"><img src="images/small/20.jpg" alt="image20" /></a></li>
		</ul>
		<!-- End Elastislide Carousel -->
	</div>
</div>

This structure is most important, because the classes added to the HTML controls are used inside the CSS and JavaScript files.
So, we just need to replace the “list items (li)” inside the “Unordered Lists” with Repeater Items, which eventually would look like the same structure and render all the image URLs inside List Items.

Step-3 : Create a Web Application and Add one aspx Page

After adding the aspx page to the Project, now we need to copy the js, css files and images from the “Downloaded Plugin” folders. So, Solution Explorer would look like…

Solution Explorer View

Solution Explorer View


NOTE : We have maintained the exact folder structure as in the Downloaded Plugin. Only “small” folder inside “images” folder is copied with another the “nav.png” image used for “previous next” buttons.

Step-4 : Let’s Design the aspx Page

Basically, we will copy the HTML present in index.html page and update it by adding one Repeater.
Now, the div would look like…

<div class="container demo-1">
	<div class="main">
		<ul id="carousel" class="elastislide-list">
			<asp:Repeater ID="mylist" runat="server">
				<ItemTemplate>
					<li><a href="#">
						<asp:Image ID="Image1" runat="server" ImageUrl='<%# "images/small/" + Eval("image")%>' />
					</a></li>
				</ItemTemplate>
			</asp:Repeater>
		</ul>
	</div>
</div>

:: Here ImageUrl Property is a combination of folders path and image name. Image Name is dynamically bound from the Datasource (explained in the next step), EVAL is used for this purpose only.
Next we will add the JavaScript and CSS files in the Page just like it appears in the index.html Page.
Now, most important thing is to add the following script inside the body.

<script type="text/javascript">
    $('#carousel').elastislide();
</script>

This code actually invokes the Slider to work. carousel is the id of the ul (Unordered list) element in HTML. This elastislide(); method is present in the Plugin js.

Step-5 : Bind the Repeater from Code Behind

protected void Page_Load(object sender, EventArgs e)
{
	if (!Page.IsPostBack)
	{
		BindRepeater();
	}
}

/// <summary>
/// This method binds the Image Slider.
/// </summary>
private void BindRepeater()
{
	DataTable dt = new DataTable();
	dt.Columns.Add("image");

	for (int i = 1; i <= 20; i++)
	{
		dt.Rows.Add(i + ".jpg");
	}

	mylist.DataSource = dt;
	mylist.DataBind();
}

This code is very simple. It binds the Repeater from a DataTable, which contains rows as image names. Image names are 1.jpg, 2.jpg till 19.jpg. You can put your image binding logic here to bind the Repeater.

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